Commitments and Contingencies, Environmental Contingencies (Details) $ in Millions	Mar. 31, 2017 USD ($) Site
Other MGP Sites [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Number of identified MGP sites under current investigation and/or remediation \| Site	2
Accrual for Environmental Loss Contingencies, Gross	$ 1.7
Minimum [Member] \| Capital Addition Purchase Commitments [Member] \| Federal Clean Water Act Effluent Limitations Guidelines [Member]
Environmental Requirements [Abstract]
Liability for estimated cost to comply with regulation	21.0
Maximum [Member] \| Capital Addition Purchase Commitments [Member] \| Federal Clean Water Act Effluent Limitations Guidelines [Member]
Environmental Requirements [Abstract]
Liability for estimated cost to comply with regulation	$ 32.0

-- None. No documentation exists for this element. --

No definition available.

Name:	psco_EnvironmentalRequirementsAbstract
Namespace Prefix:	psco_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated undiscounted amount of the accrual required to comply with required regulation.

+ References

No definition available.

+ Details

Name:	psco_LiabilityForEstimatedCostToComplyWithRegulation
Namespace Prefix:	psco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of sites where former manufactured gas plant (MGP) activities have or may have resulted in actual site contamination and are under current investigation and/or remediation.

+ References

No definition available.

+ Details

Name:	psco_NumberOfIdentifiedMgpSitesUnderCurrentInvestigationAndOrRemediation
Namespace Prefix:	psco_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Undiscounted amount of the accrual for environmental loss contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q1)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859

+ Details

Name:	us-gaap_AccrualForEnvironmentalLossContingenciesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_EnvironmentalRemediationSiteAxis=psco_OtherMgpSitesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_CapitalAdditionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	psco_EnvironmentalRegulationAxis=psco_FederalCleanWaterActEffluentLimitationsGuidelinesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: